sedimentation/siltation and habitat alteration, while likely sources include agriculture and industrial point-source discharge. Many streams in the watershed experience significant impacts due to agriculture, as heavy use of agricultural lands reduces the creek's water quality. A total of of streams, or about 83% of all the stream miles in the watershed, are impaired. The nearby Mahoning Creek is in "better environmental shape" than Chillisquaque Creek. However, in the 1980s, the concentrations of pollutants in the creek were relatively low, despite being increased by discharges from a nearby power plant. For instance, the selenium concentration was consistently under 0.010 milligrams per liter, the United States Environmental Protection Agency criterion for that pollutant. Between 1980 and 2014, the highest average annual discharge of Chillisquaque Creek at Washingtonville was , in 2011. The second-highest average annual discharge, , occurred in 1984, while the third-highest, , occurred in 2004. The lowest average annual discharge, , occurred in 2001. The second-lowest, , occurred in 1988 and the third-lowest, , occurred in 2013. The months with the highest average discharge are March, April, and December; their values are , , and , respectively. The PPL power plant contributes about of water to the creek. During several measurements in the 1970s, the pH of Chillisquaque Creek near Washingtonville ranged from 6.3 to 7.1. The specific conductance of the creek ranged from 170 to 250 micro-siemens per centimeter at . The turbidity ranged between 2 and 7 Jackson Turbidity Units. The concentration of water hardness in the creek ranged from 84 to 130 milligrams per liter. The concentration of dissolved oxygen ranged from 9.0 to 11.0 milligrams per liter, while the hydrogen ion concentration ranged from 0.00008 to 0.00051 milligrams per liter. The carbon dioxide concentration ranged between 4.7 and 49 milligrams per liter. In the 1970s, the concentration of nitrate as nitrogen in Chillisquaque Creek near Washingtonville ranged from 1.68 to 2.00 milligrams per liter, while the concentration of nitrite as nitrogen ranged from 0.040 to 0.164 milligrams per liter. The concentration of phosphorus ranged from 0.040 to 0.520 milligrams per liter. The organic carbon concentration was 3.0 milligrams per liter in one measurement. The concentration of sulfate ranged from 32.0 to 114 milligrams per liter in the creek's filtered water and the chloride concentration ranged between 8.0 and 14.0 milligrams per liter, again in filtered water. The ammonia concentration ranged from 0.026 to 0.811 milligrams per